Polishing is one of the processes for manufacturing a wafer, performed by polishing a wafer so as to reduce a thickness thereof by about 10 μm to remove damaged portions generated in a previous process and adjusting localized light scatter (LLS) and haze while minor-surface polishing a surface of the wafer.
FIG. 1 illustrates a perspective view showing a polisher according to a conventional art. Hereinafter, the polisher will be described with reference to FIG. 1.
As shown in FIG. 1, the conventional polisher includes a plate 12, a mounting block 14, a pressure plate 16, a center guide 17 and an outer guide 18.
An abrasive cloth 11 is attached to an upper surface of the plate 12, and the plate 12 is rotated at a predetermined rpm. The mounting block 14, upon which a wafer is mounted, is mounted on the plate 12. The pressure plate 16 is capable of rotating while applying a predetermined pressure to the mounting block 14. The center guide 17 and the outer guide 18 guide the mounting block 14 to be positioned right under the pressure plate 16.
When the pressure plate 16 rotates in the state of pressing the mounting block 14, polishing is performed through the interaction between the abrasive cloth 11 and a polishing solution. Since such structures are generally known and employed in the polisher 10, a detailed description thereof will be omitted.
As described above, the pressure plate 16 applies a predetermined pressure to the mounting block 14 while rotating, thereby generating friction between the wafer and the abrasive cloth 11. Polishing of the wafer is thus achieved as the friction mirror-surface polishes a surface of the wafer. Here, a central shaft 16a of the pressure plate 16 is connected to a cylinder (not shown) which adjusts the pressure of the pressure plate 16 applied to the mounting block 14.
However, the above polisher according to a conventional art has some problems as follows. FIG. 2 illustrates a view showing the pressure applied to the mounting block in which the pressure plate is mounted with the wafer in the polisher shown in FIG. 1.
In FIG. 2, arrow marks denote the degree of pressure applied by the pressure plate 16 to the mounting block 14. As shown in FIG. 2, when the pressure plate 16 applies a pressure to the mounting block 14, the pressure is greater at the center of the mounting block 14 than at the periphery of the mounting block.
To avoid such non-uniformity of the pressure, a ring pad is conventionally attached to a lower surface of the pressure plate.
FIG. 3 illustrates the pressure of a pressure plate mounted with a ring pad, applied to the mounting block. FIG. 4 illustrates an enlarged view of a portion A of FIG. 3. FIG. 5 illustrates a bottom view of the pressure plate shown in FIG. 3.
The pressure plate 19 shown in FIG. 3 to FIG. 5 is mounted with a pad 16b having a ring shape, mounted along the circumference of a lower surface thereof, so as to apply a relatively uniform pressure to the mounting block 14.
However, when using the pressure plate 19, the ring pad 16b needs to be newly manufactured for each case to have different diameters according to conditions of each case to maintain flatness of the wafer. Furthermore, if the center of the pressure plate 19 is not accurately corresponded to the center of the ring pad 16b, flatness of the wafer may be deteriorated. Also, an abrasive cloth is necessary to manufacture the ring pad 16b. 
Otherwise, the pressure of the cylinder (not shown) applied to the pressure plate 19 may be adjusted instead of changing the diameter of the ring pad 16b. In this case, however, polishing may not be uniformly performed due to variation of the pressure, accordingly causing damage to the wafer surface. That is, inferior goods may be produced.